Several studies have shown that people with HIV are at greater risk for bone loss, but it is not clear whether this is due to HIV infection itself, resulting inflammation or metabolic abnormalities, toxicities of antiretroviral drugs, or a combination of factors. Hepatitis C has also been linked to bone loss, suggesting that HIV/HCV coinfected people may be particularly susceptible. However, the relationship between bone loss and fractures in this population is not well understood.

Vincent Lo Re from the University of Pennsylvania and colleagues sought to determine whether people with hepatitis C infection alone are at increased risk for hip fractures compared with uninfected individuals, and to examine if the risk is higher among HIV/HCV coinfected patients compared to those with HCV alone, HIV alone, or neither.

The researchers prospectively analyzed a cohort of people receiving Medicaid in California, Florida, New York, Ohio, and Pennsylvania during 1999-2005. Within this group 95,827 had only HIV; 276,901 had only HCV; 36,950 were coinfected; and 3,110,904 were uninfected.

Participants with HCV alone were older on average and more likely to be women compared with the HIV monoinfected and HIV/HCV coinfected groups. People with HCV monoinfection also had more conditions associated with bone loss, including heavy alcohol consumption, cardiovascular disease, diabetes, and kidney disease.

Results

· The incidence rate of hip fractures was lowest for people with neither HIV nor HCV, at 1.29 events per 1000 person-years.

· People with HIV alone had a higher incidence than the uninfected group, at 1.95 events per 1000 person-years.

· People with HCV alone had an even higher incidence, 2.69 events per 1000 person-years.

· Participants coinfected with HIV and HCV had the highest risk, with an incidence rate of 3.06 events per 1000 person-years.

· In a multivariate analysis adjusting for other factors, HIV/HCV coinfection was associated with an increased relative risk of hip fracture compared with the other 3 groups:

· HCV monoinfection was associated with an increased hip fracture risk compared with uninfected individuals, with the greatest relative increase seen in the youngest age groups (adjusted HR 3.56 for women and 2.40 for men age 18-39 years).

Based on these findings, the study authors concluded, "Among Medicaid enrollees, HCV/HIV coinfection was associated with increased rates of hip fracture compared to HCV-monoinfected, HIV-monoinfected, and HCV/HIV-uninfected persons. HCV-monoinfected patients had an increased risk of hip fracture compared to uninfected individuals."

Hypothesizing about the reasons for this risk difference in their discussion, the researchers proposed that inflammation associated with chronic viral infection might promote bone loss, but also suggested and that antiretroviral therapy and lifestyle factors common in this population -- including heavy alcohol or drug use, smoking, and poor nutrition -- likely also play a role.